Molecular Pharmacology, Vol 17, 374-381, Copyright © 1980 by the American Society for Pharmacology and Experimental Therapeutics

An Immunohistochemical Study on the Localization and Distribution of NADPH-Cytochrome c (P-450) Reductase in Rat Liver

¹ The Toxicology Center, Department of Pharmacology, College of Medicine, The University of Iowa, Iowa City, Iowa 52242

The localization and distribution of NADPH-cytochrome c (P-450) reductase (NADPH: ferricytochrome oxidoreductase; EC 1.6.2.4) were investigated immunohistochemically in the livers of untreated rats employing both an unlabeled antibody peroxidase—antiperoxidase technique and an indirect fluorescent antibody method. The immunohistochemical localization of the reductase was accomplished through the use of sheep antiserum produced against NADPH-cytochrome c reductase which had been purified from hepatic microsomes of phenobarbital-pretreated rats. In both immunohistochemical procedures, staining for the reductase was detected in hepatocytes throughout the liver, although differences were noted in the intensity of immunostaining of hepatocytes within the liver lobule. Employing the indirect fluorescent antibody immunohistochemical staining method, the extents of binding of the antireductase to hepatocytes within the three regions of the liver lobule were determined. While hepatocytes within the centrilobular and midzonal regions bound the antireductase to similar extents, hepatocytes within the periportal regions of the lobule bound significantly less antireductase. Similar patterns of intralobular distribution for the antireductase were observed in the livers of male and female rats. Further, similar patterns of immunohistochemical staining for the reductase within the liver lobule were observed in the right, median, left, and caudate lobes. The results of this study thus demonstrate that NADPH-cytochrome c (P-450) reductase is not distributed uniformly throughout the liver lobule.

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ACKNOWLEDGMENTS The authors would like to express their thanks to Drs. Gordon F. Kapke, Phillip Greenspan, and Thomas K. Shires for their helpful suggestions. The technical assistance of Mrs. Cheryl Standing Eckart is gratefully acknowledged.